From the Susan Blake interview, Obama’s mama comes across as pretty much clueless. I’m not sure how she would have traveled with child and run around for two or three weeks and not be more capable. This is what makes me think the baby was adopted in Washington. Of course, there are no actual baby pictures anywhere to be found.
If she had just arrived from Kenya, she also migh have known little about caring for an infant. If it is true that he was born in Kenya (which I am inclined to think is the truth), she would have stayed at the hospital for some days - usually in the US at that time it was 5 days, who know what it was there - and then gotten a plane as fast as she could. Maybe others were taking care of the infant 0kaka until she left.